FAS and toxic epidermal necrolysis: The caspase system itself is in TEN patients triggered either through binding of a specific ligand (FasL, CD95L) to a receptor (FasR, CD95R, APO-1, TNFRSF6) or through TNFα binding to a specific receptor (TNFR1, Tumor Necrosis Factor Receptor 1) (Locksley et al., 2001; Lavrik and Krammer, 2012).